Lennox signed with the Boston Red Sox for a $100,000 bonus in August 2006. He hit .333/.364/.476 in the 2008 Claxton Shield but was 0-2 with a 9.35 ERA on the hill. He made his minor league debut with the 2008 GCL Red Sox, used as a pitcher despite his better hitting than pitching back in Australia. He was 2-3 with a 3.94 ERA in eight outings, walking only two in 16 innings.

In the 2009 Claxton Shield, he walked five and allowed one run in 1 2/3 innings. Back with the GCL Red Sox that summer, the right-hander went 2-2 with a save and a 3.47 ERA and again showed better control than he had in Australia, with only two free passes in 23 1/3 innings. Despite a 3.66 ERA after two minor league seasons, the Red Sox cut him loose in the off-season.